Impact wrench

ABSTRACT

A rotary impact wrench transmits its impacts through a torsion unit with variable spring characteristics. The torsion unit comprises a torsion bar that is inserted into a sleeve with a selectively variable part of its length protruding from the sleeve.

United States Patent .1 1

Schoeps Sept. 3, 1974 IMPACT WRENCH 2,654,234 10/1953 Christensen 64/6[75] I entor: Knu Christ an Schoeps, Nac a, Reynolds 81/52.3

- Sw d 2,964,981 12/1960 t 3,129,571 4/1964 [73] Asslgnee' g gzggAkt'ebolag Nacka 3,306,639 2/1967 Lyon 21/177 A [22] Filed: Jan. 24,1973 Primary Examiner-James L. Jones, Jr. 1 pp N011 3261526 Attorney,Agent, or Firm-Flynn & Frishauf [30] Foreign Application Priority DataJan. 31, 1972 Sweden 1047/72 [57] ABSTRACT [52] US. Cl. 81/52.3 A rotarymp re c transmits its impacts through [51] Int. Cl B251) 19/00 a torsionunit with variable spring chara t ristics. The [5 1 Field Of Search403/107, 108; 81/52 3, =torsion unit comprises a torsion bar that isinserted 31/177 A; 64/4, 3, 6 into a sleeve with a selectively variablepart of its length protruding from the sleeve. [56] References CitedUNITED STATES PATENTS 13 Claims, 4 Drawing Figures 2,438,633 3/1948Condor 81/177 A ae-m a s IMPACT WRENCH This invention relates to animpact wrench with an anvil to which a rotating hammer appliesintermittent torque that is transmitted to a nut or the like through atorsion unit which comprises a sleeve and a torsion bar conjointlyrotating with the sleeve, the effective length and thereby the effectivespring characteristics of the torsion bar being variable.

In a prior form of such a wrench, the torsion bar is axially fixedlymounted in the sleeve and protrudes from the sleeve only with a drivesquare. The torque is transmitted from the sleeve to the bar through amember which is non-rotatable to but in sliding connection with thesleeve as well as with the bar. This design gives relatively largelosses in impact energy as compared with a design with a non-adjustabletorsion bar.

It is therefore an object of the invention to provide for a nut runnerwith an adjustable torque transmitting torsion unit which gives smalllosses. This is provided for by a torsion unit' which includes only onesliding connection, this connection giving a so called slendertransmittance of the torque. To this end the invention has been giventhe characteristics stated in the claims.

The invention will be further described with reference to theaccompanying drawings which show two embodiments of the invention.

FIG. 1 is a longitudinal section through the forward portion of awrench,

FIG. 2 is a cross section at an enlarged scale taken along lines 2-2 inFIG. 1,

FIG. 3 is a longitudinal section through the forward portion of anotherwrench, and

FIG. 4 is a cross section at an enlarged scale taken along line 4-4 inFIG. 3.

In FIG. 1, the housing of the impact wrench is generally denoted by 11.A drive square 12 protrudes from the housing 11 and it is an integralpart of an anvil 13 which has radial anvil surfaces 14. A rotatinghammer 15 has impact dogs 16, and it is rotated by a pneumatic slidingvane motor or any other suitable type of motor. The hammer or a part ofthe hammer has besides its rotating movement also a simultaneous axialmovement so that the impact dogs 16 will repeatedly strike (applyintermittent torque to) the anvil surfaces 14 of the anvil at a rate offor instance 2,000 impacts per minute. The drive square 12 is insertedin the rearward end of a sleeve 17 and is axially locked by means of aresiliently mounted pin 18 which protrudes radially from the drivesquare. The sleeve 17 has through interior axial splines 19 whichregister with corresponding external splines 20 on the torsion bar 21.The free end of the torsion bar 21 is formed as a drive square 22 onwhich a nut socket 23 is attached by means of a resiliently mounted pin24. The bar 21 has a radial hole 25 which canalign with any of fourholes 26 in the sleeve 17 since the rodis axially slidable in thesleeve. The bar and the sleeve can be axially interlocked by means of apin 27 as shown in the figures. The pin 27 is retained by means of aspring plate 28. The pin 27 should have a clearance to the holes 25,26so that it cannot be subjected to the torque that is transmitted by thespline connection 19,20. With respect to its elastic properties, thetorsion unit 17,21 can be divided into three portions, namely: theprotruding part of the torsion bar 21, the stiff portion of the splineconnection 19,20, and the part of the sleeve 17 which is above the endof the bar 21 and has an elasticity of for instance one tenth of theelasticity of the bar. Thus, by selectively varying the length of theprotruding portion of the bar, the operator can vary the total springcharacteristics of the torsion unit 17,21 within wide limits.

In FIGS. 3 and 4, details which correspond to details in FIGS. 1 and 2have been given the same reference numerals as in the latter figures.The anvil 13 ends in this modification with a hexagonal recess 30, andthe bar 21 has a corresponding hexagonal cross section. The bar isinserted in the hexagonal recess with one end and it is axially retainedby a ball 31 which register with an annular recess 32 in the bar. Theball 31 is held in place by a spring loaded axially movable retainersleeve 33. The sleeve 17 has also hexagonal interior cross section whichregisters with the exterior hexagonal form of the bar, and the bar 21and the sleeve 17 can be moved axially relative to each other andinterlocked by means of a pin 27 in the same way as described withreference to FIGS. 1 and 2. The lower end of the sleeve 17 is formed asa socket 34 for anut, but, of course, it can instead be formed as adrive square for a nut socket of the type shown in FIG. 1.

What I claim is:

1. An impact wrench comprising:

an anvil,

a power rotated hammer adapted to apply rotary impacts to the anvil, and

a torsion unit coupled to said anvil for transmitting from said anvilsaid rotary impacts as intermittent torque to a nut or the like, saidtorsion unit comprising:

a torsion bar and a sleeve, said sleeve slidably receiving said torsionbar therein from one end with said torsion bar being non-rotatablerelative to said sleeve, said one end forming with said torsion bar atorque transmitting joint, and

means for axially interlocking said torsion bar and said sleeve with aselectively variable part of the length of said bar protruding from saidjoint, the torque transmission characteristics of said torsion unitbeing a function of the degree of protrusion of said torsion bar fromsaid joint.

2. A wrench according to claim 1 in which said sleeve is affixed to saidanvil, and said torsion bar has a free end protruding from said sleeve.

3. A wrench according to claim 1 in which said torsion bar is affixed tosaid anvil, and said sleeve has a free end.

4. A wrench according to claim 3 in which the free end of said sleeve isformed as a socket for a nut.

5. A wrench according to claim 1 in which said torsion bar has agenerally circular cross section and is provided with a number of axialsplines, and said sleeve has a number of axial splines which registerwith said axial splines in said torsion bar to prevent relative rotationof said torsion bar and sleeve.

6. A wrench according to claim 1 in which said axially interlockingmeans includes recesses formed in said sleeve and said torsion bar, saidrecesses being adapted to receive a locking element therein so as toaxially interlock said sleeve and said torsion bar.

7. A wrench according to claim 6 in which said recesses are radial holesin said sleeve and said torsion bar, and said locking element comprisesa locking pin adapted to be radially inserted in said radial holes insaid sleeve and said torsion bar.

8. A wrench according to claim 5 in which said splines of said sleeveare through splines.

9. A wrench according to claim 6 in which said torsion bar has a singlerecess and said sleeve has a plurality of axially spaced recesses.

10. A wrench according to claim 1 in which said torsion bar has a recessat the end thereof that is disposed inside said sleeve, and said axiallyinterlocking means includes means for engaging with said recess in saidtorsion bar to axially lock said torsion bar in said sleeve inselectively variable axial positions therebetween.

11. A wrench according to claim 2 wherein said free end of said torsionbar includes means for coupling said rotary impacts to said nut or thelike,

12. A wrench according to claim 6 in which a clearance is providedbetween said locking pin and said radial holes.

13. A wrench according to claim 12 in which said torsion bar has agenerally circular cross section and is provided with a number of axialsplines, and said sleeve has a number of axial splines which registerwith said axial splines in said torsion bar to prevent relative rotationof said torsion bar and sleeve. a l

1. An impact wrench comprising: an anvil, a power rotated hammer adaptedto apply rotary impacts to the anvil, and a torsion unit coupled to saidanvil for transmitting from said anvil said rotary impacts asintermittent torque to a nut or the like, said torsion unit comprising:a torsion bar and a sleeve, said sleeve slidably receiving said torsionbar therein from one end with said torsion bar being non-rotatablerelative to said sleeve, said one end forming with said torsion bar atorque transmitting joint, and means for axially interlocking saidtorsion bar and said sleeve with a selectively variable part of thelength of said bar protruding from said joint, the torque transmissioncharacteristics of said torsion unit being a function of the degree ofprotrusion of said torsion bar from said joint.
 2. A wrench according toclaim 1 in which said sleeve is affixed to said anvil, and said torsionbar has a free end protruding from said sleeve.
 3. A wrench according toclaim 1 in which said torsion bar is affixed to said anvil, and saidsleeve has a free end.
 4. A wrench according to claim 3 in which thefree end of said sleeve is formed as a socket for a nut.
 5. A wrenchaccording to claim 1 in which said torsion bar has a generally circularcross section and is provided with a number of axial splines, and saidsleeve has a number of axial splines which register with said axialsplines in said torsion bar to prevent relative rotation of said torsionbar and sleeve.
 6. A wrench according to claim 1 in which said axiallyinterlocking means includes recesses formed in said sleeve and saidtorsion bar, said recesses being adapted to receive a locking elementtherein so as to axially interlock said sleeve and said torsion bar. 7.A wrench according to claim 6 in which said recesses are radial holes insaid sleeve and said torsion bar, and said locking element comprises alocking pin adapted to be radially inserted in said radial holes in saidsleeve and said torsion bar.
 8. A wrench according to claim 5 in whichsaid splines of said sleeve are through splines.
 9. A wrench accordingto claim 6 in which said torsion bar has a single recess and said sleevehas a plurality of axially spaced recesses.
 10. A wrench according toclaim 1 in which said torsion bar has a recess at the end thereof thatis disposed inside said sleeve, and said axially interlocking meansincludes means for engAging with said recess in said torsion bar toaxially lock said torsion bar in said sleeve in selectively variableaxial positions therebetween.
 11. A wrench according to claim 2 whereinsaid free end of said torsion bar includes means for coupling saidrotary impacts to said nut or the like.
 12. A wrench according to claim6 in which a clearance is provided between said locking pin and saidradial holes.
 13. A wrench according to claim 12 in which said torsionbar has a generally circular cross section and is provided with a numberof axial splines, and said sleeve has a number of axial splines whichregister with said axial splines in said torsion bar to prevent relativerotation of said torsion bar and sleeve.